About two minutes before the noodles are fully cooked I added about a cups worth of frozen peas to the noodles. Yes I know this slows the cooking time down but I do it anyway - my bad. NOTE: If you are going to use canned peas add them to the noodles when you add the tuna otherwise they will be way mushy. ALSO if you are using canned peas you will want to drain them and rinse them well before adding to the noodles to reduce the salt content and that oh so special can flavor.
Add cheese and butter to the noodles, peas and tuna. Mix until butter is melted over low heat try not to scorch/burn you macaroni.